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<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>多类名使用方式</title>
    <style>
        /* id选择器的口诀：样式#定义，结构id调用，只能调用一次，别人切勿使用 */
        #green {
            color: green;
        }

    </style>
</head>

<body>
    <div id="green">刘德华</div>
    <div>刘德华</div>

    
</body>
</html>